Same-day fluorescence confocal microscopy of MRI-targeted prostate biopsies: A feasibility study

To determine the diagnostic performance of ex vivo fluorescence confocal microscopy (FCM) for prostate cancer detection in magnetic resonance imaging (MRI)-targeted biopsy specimens using final histopathology as the reference standard, and to quantify workflow component times relevant to same-day implementation.

In this single-centre prospective observational study, men undergoing MRI-targeted transperineal prostate biopsy were enrolled. Targeted biopsy cores were imaged ex vivo using a Histolog® FCM scanner (SamanTree Medical SA, Lausanne, Switzerland) after rapid acridine orange immersion and prior to routine histopathological processing. Two board-certified genitourinary pathologists independently reviewed FCM images in a blinded fashion and classified each specimen as positive or negative for prostate cancer and clinically significant cancer (CSC), defined as International Society of Urological Pathology Grade Group (GG) ≥2. Diagnostic performance was calculated against final histopathology. Workflow feasibility was assessed by measuring specimen preparation, scanning, and interpretation times. Interobserver agreement and exploratory discordance analyses were performed.

A total of 50 MRI-targeted biopsy specimens from 44 patients were analysed, of which 33 (66%) contained prostate cancer and 17 (52%) met criteria for CSC. For cancer detection, Reader 1 achieved 87.9% sensitivity and 94.1% specificity, and Reader 2 achieved 97.0% sensitivity and 76.5% specificity, with overall accuracy of 90% for both readers. Interobserver agreement for cancer detection was 88% (κ = 0.74), and for CSC was 86% (κ = 0.61). Mean specimen preparation and interpretation times were ~2 min each, with standardised scanning time of 50 s, enabling complete FCM assessment in <5 min per target. Discordance was concentrated in GG 2 disease and Prostate Imaging-Reporting and Data System (PI-RADS) 3 targets, while higher-grade cancers and PI-RADS 5 lesions were uniformly concordant.

Ex vivo FCM provides rapid, accurate, and reproducible assessment of MRI-targeted prostate biopsy specimens for cancer detection within clinically feasible timeframes. These findings support FCM as a same-day diagnostic adjunct and justify prospective trials evaluating real-time implementation during targeted biopsy.